Asparagus spears rising from the soil are an edible announcement of spring’s arrival. Because this is a perennial crop, a well-nurtured asparagus planting can yield a bounty of tasty asparagus season after season.
Start with a full-sun location for your asparagus bed, with well-draining soil. You can expect your planting to produce for at least a decade, so make sure its location won’t interfere with other plantings (tall ferns may cast shade). I find that an asparagus bed makes an attractive garden border.
Asparagus plants are heavy feeders that perform best in deep, fertile soils. Once you select a site, begin soil improvement with a soil test. Chances are, you will need to add lime, because asparagus prefers a slightly higher pH than most vegetables. You may also need to add phosphorous or potassium before planting.
Enrich your soil with a generous portion of high-quality organic matter like compost, leaf mold or aged manure. If your soil is heavy clay, consider double digging to break up the subsoil and increase the rooting depth to 20 inches or more. If possible, finish bed preparation six to 12 months before planting.
Asparagus plants are either male or female. Female varieties, such as Mary and Martha Washington, produce larger spears. But male varieties, such as Jersey Knight, Jersey Supreme and Jersey Giant, are generally preferred, because they produce more spears of smaller diameter and don’t develop seeds, which may become weedy.
It is possible to grow asparagus from seeds, but starting with one-year-old crowns or plants gives you a head start. Late winter is the ideal planting time—beginning in early January on the coast and ending by late March in the Upstate. Your local garden center can tell you when crowns will be available.
With soil prepared and crowns in hand, it’s time to plant! Dig a trench 6 to 8 inches deep in the prepared bed, and create a slight mound in the bottom. Space the crowns 15 inches apart, and spread their roots over the mound. Cover the crowns and roots with 2 inches of soil. Water to settle the soil around the crowns. Add 2 inches of soil every two to three weeks as the spears grow until the trench is filled. Keep watering as needed.
Here’s the hard part: Resist the temptation to harvest spears the first two seasons after planting. Your plants need two full growing seasons to develop a strong root system and vigorous crown. You can begin enjoying the fruits of your labor in the third spring, harvesting six to eight spears daily for three weeks. The fourth year, you should be able to harvest for a full six to eight weeks.
At the end of those weeks, when the spears are reduced to pencil diameter, the harvest is over for the year. Allow the remaining spears to mature to their full height, with developed foliage known as ferns. If you remove asparagus ferns during the growing season, your future harvests will be decreased. Wait until the foliage turns completely brown during the winter, then cut the dead ferns down to 2-inch stubs.
Care after planting means fertilizing, mulching and weeding the beds. Soil tests will tell you how to fertilize your asparagus annually; apply half the fertilizer before the spears emerge and half after harvest. Top-dress the bed with compost yearly to keep organic matter high, and maintain a 2- to 3-inch layer of mulch to prevent weeds.
Asparagus plantings are a long-term investment. Spending that extra effort will reward you with spears for years.
S. CORY TANNER is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. Contact him here.
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